The aim of this project is to understand thalamocortical and corticocortical connections. Although many details concerning the anatomy of thalamocortical and corticocortical neurons are known, few physiological experiments have studied the dynamic properties of thalamocortical networks. This project is a continuation of studies that have successfully measured the functional strength of connections between anatomically-connected brain neurons using basic sensory stimulation techniques. In this project we propose experiments to elucidate the behavior of a network of thalamic and cortical neurons during more naturalistic stimulation and determine how selective loss of sensory input alters neuronal interactions in these regions. We will test the hypothesis that a moving cutaneous stimulus enhances thalamocortical and corticocortical synchrony in the somatosensory system as measured by cross-correlation analysis. They will accomplish this aim by measuring and comparing the strength of thalamocortical and corticocortical interactions produced by cutaneous RFs with stationary and moving stimuli. They will test the hypothesis that plasticity of thalamocortical circuits contribute towards cortical reorganization following temporary or permanent loss of cutaneous inputs. This will be accomplished by chronically implanting arrays of microwire electrodes into thalamus and measuring changes in the topographical organization of thalamus produced by cutaneous anesthesia or by transection of the digital nerves. They will test the hypothesis that corticocortical interactions between sensory-deprived and surrounding cortical regions become stronger during the process of cortical reorganization. This will be accomplished by inserting recording electrodes at regular intervals in the transition from innervated to sensory deprived cortical representations and using cross-correlation analysis and electrical microstimulation to measure the horizontal spread of neuronal activity. This project is concerned with uncovering fundamental principles of governing corticocortical interactions and may shed light on the mechanisms of cortical recruitment and other phenomenon involved in the etiology and development of cortical seizures. Furthermore, experiments in this project will examine changes in neuronal communication following sensory deprivation and will advance our understanding of functional recovery from nerve injury or other forms of damage to the peripheral or central nervous system.